Updated July 1, 2026
Work out your volume first
Yards and bag count before you order a single thing.
Pouring a slab is a sequence: plan and permit, prep a compacted gravel base, build square forms, set reinforcement, place the concrete, then screed, float, edge, joint, and cure. The work that decides whether the slab lasts happens before any concrete shows up.
1. Plan and check permits
Start with the purpose. A shed pad, a patio, and a garage floor have different thickness and reinforcement needs, so settle on size and use first. Four inches is the standard thickness for patios, sheds, and walkways; bump it to 5 or 6 inches for anything carrying vehicle weight. See our concrete slab thickness guide for the breakdown by use. Then call your local building department. Many slabs need a permit, and most jurisdictions want you to mark underground utilities before you dig. In the U.S. that call is free through 811. Skipping it can hit a gas or power line.
2. Gather tools and materials
Have everything on site before the concrete arrives, because once it is placed the clock does not stop. The short list: shovels, a plate compactor (rentable), a screed board, a bull float, a hand or magnesium float, an edger, a groover for control joints, a steel trowel, a wheelbarrow, and gloves and rubber boots. For materials you need crushed stone for the base, form lumber (2x4 for a 4-inch slab, 2x6 or larger for thicker pours), stakes, rebar or welded wire mesh, and either bagged concrete or a ready-mix order. Sheet plastic or a curing compound covers the final step.
3. Prepare the subgrade and gravel base
Dig out the area to depth, allowing for both the slab thickness and the gravel under it. Strip off topsoil and organic material, since those rot and settle. On clay or soft soil, remove enough to fit 6 to 8 inches of gravel; on firm soil 4 to 6 inches is enough. Spread crushed stone in even layers, rake it level, and run a plate compactor over it. Compacting in lifts matters: a well-compacted base is what stops most settlement cracks later. Check the volume of stone you need with the gravel for concrete base guide so you order the right amount.
4. Build the forms
Forms hold the wet concrete to shape and set your finished height. Set the form boards on edge around the perimeter, level them or pitch them slightly for drainage, and drive stakes every 2 to 3 feet on the outside. Screw or nail the boards to the stakes so they will not bow when the concrete pushes against them. Check the form for square by measuring the diagonals; equal diagonals mean square corners. Coat the inside faces with form-release oil or a light spray so the boards strip clean after the pour.
5. Set rebar or wire mesh
Reinforcement controls cracking. For driveways, garage floors, and load-bearing slabs, lay a grid of rebar or roll out welded wire mesh. The steel needs to sit in the middle third of the slab thickness, not on the ground, so prop it up on small supports called chairs. Tie rebar at the intersections so the grid stays put during the pour. Our rebar calculator sizes the grid and tells you how much bar to buy. Light-duty slabs sometimes skip steel, but reinforcement is cheap insurance against cracks.
6. Order ready-mix or plan to mix bags
Now nail down the quantity. Run your length, width, and thickness through the concrete calculator, then add 5 to 10 percent for waste and uneven base. Under about half a cubic yard, bagged concrete mixed on site is workable. Above one cubic yard, order ready-mix and have it delivered, because hand-mixing that much invites a cold joint, the weak seam that forms where fresh concrete meets concrete that has already started to set. Ready-mix plants often have a minimum load and a short-load fee, so confirm both when you book the truck. Line up enough helpers; even a modest patio pour needs three or four people to place and finish before it stiffens.
7. Place the concrete
Start in the far corner and work back toward your exit so you are never trapped on fresh concrete. Move it into place with a shovel or come-along, do not let it pile up and segregate, and push it into the form corners and against the edges. If you have a vibrator, use it lightly to knock out air pockets, especially along the forms. Fill to slightly above the top of the form so you have material to screed off.
8. Screed, float, edge, and joint
This is where the surface is made, and it happens fast. Work in order:
- Screed. Drag a straight board across the top of the forms with a sawing motion to strike off the excess and level the surface to the form height.
- Bull float. Push and pull a bull float across the screeded surface to flatten ridges and push down stones. Keep the leading edge slightly raised so it does not dig in. Overlap each pass.
- Wait for bleed water. A sheen of water rises to the surface. Do not touch the concrete until that sheen is gone, or you will seal water into the surface and weaken it.
- Edge. Run an edging tool along the forms to round the edges so they will not chip.
- Joint. Cut control joints with a groover, spaced roughly 24 to 30 times the slab thickness in feet, so a 4-inch slab gets joints about every 8 to 10 feet. Joints give cracks a planned place to form.
- Final finish. Hand-float or steel-trowel for a smooth surface, or drag a broom across for a non-slip texture. Broom finishes are standard for driveways and outdoor slabs.
9. Cure the slab
Curing is the step people rush, and it is the one that builds strength. Keep the slab damp for the first several days while the cement hydrates. You can mist and cover it with plastic sheeting, keep wet burlap on it, or spray a curing compound that seals moisture in. Plan on foot traffic at 24 to 48 hours, light vehicle loads around 7 days, and full design strength at 28 days. The slower the slab loses water early, the stronger it ends up. Our guide on how long concrete takes to cure walks through the full timeline.
Work out your volume first
Yards and bag count before you order a single thing.
Sources: Base depth, forming, and finishing steps follow Family Handyman, How to Form and Pour a Concrete Slab. Strength and curing timelines are from the National Precast Concrete Association, The 28-Day Myth of Concrete Curing.